1. Field of the Invention
This invention relates to inside blowout preventer for use in drilling oil and gas wells. More particularly, the invention relates to apparatus for rapidly attaching a blowout preventer sub having lower male threads to the female threads of a drill pipe.
2. Description of the Prior Art
In drilling oil and gas wells where high pressure zones are likely to be encountered, drilling companies include equipment for closing in a well if a blowout occurs or becomes eminent. The usual drilling procedure is to drill a short distance from the earth's surface such as 200 feet or so and set larger diameter casing which is referred to as surface pipe. Drilling is then continued through the large diameter surface pipe and downward to the maximum depth desired, which may be to great depths exceeding 20,000 feet. Operators typically include blowout preventer devices which are supported at the upper end of the surface pipe and which can be closed to clamp around the exterior of drill pipe in the event of blowout so as to prevent fluid and gases, including drilling mud and materials from the borehole from being blown out in the event a high pressure zone is encountered. Such blowout preventers are a common expedient and are well known.
In addition to closing around the exterior of the drill pipe to prevent the blowout around the annular area between the drill pipe and the interior of the surface pipe, it is also necessary to close off the interior of the drill pipe. Drill pipe for rotary drilling is always tubular since drill mud must be circulated downwardly through it during drilling operations. When high pressure formations are encountered, the same pressure applied to expelled drill mud, fluid and gases externally of the drill pipe is applied to the interior of the drill pipe and therefore some means must be provided for closing the interior of the drill pipe. Such devices are referred to as inside blowout preventers.
The method most commonly practiced for providing inside blowout prevention is the use of a device called an inside blowout sub. Such devices are in effect short lengths of drill pipe which have a male thread on the lower end dimensioned to threadably engage the female thread on the upwardly extending upset end of the drill pipe. The sub has a corresponding female thread on the upper end. The outside diameter is no greater than the outside diameter of the upset end of the drill pipe for which the sub is to be used. Thus after the blowout sub is attached another length of drill pipe may be attached to it and drilling continued or well control actions initiated.
There are two basic types of blowout subs, both of which have the same exterior configuration. In one type a check valve is employed. This functions to prevent flow of fluid from within the drill pipe but permit flow of fluid downwardly into the drill pipe. A second type employs the use of an internal valve which may be opened and closed externally of the sub. This arrangement permits the sub to be opened or closed according to the desire of the operator.
In the present technique the blowout sub is manually positioned in place over the drill pipe and stabbed so that the sub may be rotated to threadably connect it with the drill pipe. Since blowout subs are relatively heavy (approximately 200 pounds for typical 5" o.d. drill pipe), they are very difficult to manually handle. Usually blowout preventer subs are suspended by a cable which extends over a pulley in the drilling derrick. A counterweight is attached to the other end of the cable. This helps provide lifting support for the blowout preventer sub, and if there is no blowout conditions taking place, the sub can be positioned by workmen over the drill pipe and rotated into threaded engagement with the pipe. On the other hand, if blowout is occurring in which fluid, gases or drilling mud may be rapidly discharged from the interior of the drill pipe, it is exceedingly difficult for workmen to manually position the sub over the drill pipe and lower it into positon for threaded engagement. Obviously the more violent the blowout, the more difficult is the job of stabbing and threading a blowout sub onto a drill pipe.
The present invention is directed towards a device for rapidly positioning, stabbing and rotating an inside blowout preventer sub to a drill pipe to thereby eliminate the problems existing with the present system of manually positioning the blowout sub for attachment.
It is therefore an object of the present invention to provide an improved inside blowout preventer for a drill pipe.
More particularly, an object of the invention is to provide an apparatus for rapidly attaching an inside blowout preventer sub having a lower male thread end to the upper female threaded end of a drill pipe.
Still more particularly, an object of the present invention is to provide a device for removable attachment to an inside blowout preventer sub and including means whereby the device can be rapidly positioned on the upper end of a length of drill pipe and manually actuated to bring the blowout preventer sub into alignment for threadably attaching the sub to the drill pipe, after which the mechanism may be expeditiously removed from the drill pipe and sub permitting further drilling operations.